1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly relates to a semiconductor device capable of switching a bias current flowing along a bias line.
2. Description of Related Art
There are cases that a semiconductor device switches the amount of a bias current flowing along a bias line. As an example, a type of duty-cycle control circuit that controls a duty cycle of a clock signal has a function to change a duty cycle based on a bias current (see Japanese Patent Application Laid-open No. 2009-65633). In such a type of duty-cycle control circuit, a feedback control of changing the amount of the bias current that flows along the bias line in response to the present duty cycle of the clock signal is conducted for the purpose of stabilizing the duty cycle of the clock signal to a desired value (typically, 50%).
However, changing a bias current that flows along a bias line can cause generation of noise on the bias line due to on and off of a switch. In this case, noise is generated whenever the bias current is changed. If such noise is generated in the above-mentioned duty-cycle control circuit which changes a duty cycle based on a bias current, there is a risk that the duty-cycle control circuit cannot stabilize the duty cycle of the clock signal to a desired value.